arXiv subjects

Y. Ding

Publications and source records attributed to Y. Ding.

At least 829 records · Page 46Linked to original sources

arXiv2014

Measurement of the branching fraction for $ψ(3686)\toωK^+ K^-$

With $1.06\times 10^8$ $ψ(3686)$ events collected with the BESIII detector, the branching fraction of $ψ(3686) \to ωK^+ K^-$ is measured to be $(1.54 \pm 0.04 \pm 0.11) \times 10^{-4}$. This is the most precise result to date, due to the largest $ψ(3686)$ sample, improved signal reconstruction efficiency, good simulation of the detector performance, and a more accurate knowledge of the continuum contribution. Using the branching fraction of $J/ψ\to ωK^+ K^-$, the ratio $\mathcal{B}(ψ(3868) \to K^+K^-) / \mathcal{B}(J/ψ\to K^+K^-)$ is determined to be $(18.4 \pm 3.7)\,\%$. This constitutes a significantly improved test of the $12\,\%$ rule, with the uncertainty now dominated by the $J/ψ$ branching fraction.

hep-ex↗

arXiv2014

Observation of Electromagnetic Dalitz decays J/ψ\to P e^+e^-

Based on a sample of (225.3\pm2.8)\times 10^{6} J/ψevents collected with the BESIII detector, the electromagnetic Dalitz decays of J/ψ\to P e^+e^-(P=η'/η/π^0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/ψ\to η' e^+e^-, J/ψ\to ηe^+e^- and J/ψ\to π^0 e^+e^- are observed for the first time. The branching fractions are determined to be \mathcal{B}(J/ψ\to η' e^+e^-) = (5.81\pm0.16\pm0.31)\times10^{-5}, \mathcal{B}(J/ψ\to ηe^+e^-) = (1.16\pm0.07\pm0.06)\times10^{-5}, and \mathcal{B}(J/ψ\to π^0 e^+e^-)=(7.56\pm1.32\pm0.50)\times10^{-7}, where the first errors are statistical and the second ones systematic.

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arXiv2014

Observation of $η^{\prime}\toπ^{+}π^{-}π^{+}π^{-}$ and $η^{\prime}\toπ^{+}π^{-}π^{0}π^{0}$

Using a sample of $1.3\times 10^9$ $J/ψ$ events collected with the BESIII detector, we report the first observation of $η^{\prime}\toπ^{+}π^{-}π^{+}π^{-}$ and $η^{\prime}\toπ^{+}π^{-}π^{0}π^{0}$. The measured branching fractions are $\mathcal{B}$($η^{\prime}\toπ^{+}π^{-}π^{+}π^{-}$) = $(8.53\pm0.69({\rm stat.})\pm0.64({\rm syst.}))\times10^{-5}$ and $\mathcal{B}$($η^{\prime}\toπ^{+}π^{-}π^{0}π^{0}$) = $(1.82\pm0.35({\rm stat.})\pm0.18({\rm syst.}))\times10^{-4}$, which are consistent with theoretical predictions based on a combination of chiral perturbation theory and vector-meson dominance.

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arXiv2014

Search for the rare decays $J/ψ\to D_s^-ρ^+$ and $J/ψ\to \overline{D}{}^0\overline{K}{}^{\ast0}$

A search for the rare decays of $J/ψ\to D_s^-ρ^+ + c.c.$ and $J/ψ\to \overline{D}{}^0\overline{K}{}^{\ast0} + c.c.$ is performed with a data sample of 225.3 million $J/ψ$ events collected with the BESIII detector. No evident signal is observed. Upper limits on the branching fractions are determined to be $\mathcal{B}(J/ψ\to D_s^-ρ^+ + c.c.) < 1.3 \times 10^{-5}$ and $\mathcal{B}(J/ψ\to \overline{D}{}^0\overline{K}{}^{\ast0} + c.c.) < 2.5 \times 10^{-6}$ at the $90\%$ confidence level.

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arXiv2014

Observation of a charged charmoniumlike structure in $e^+e^- \to (D^{} \bar{D}^{})^{\pm} π^\mp$ at $\sqrt{s}=4.26$GeV

We study the process $e^+e^- \to (D^{*} \bar{D}^{*})^{\pm} π^\mp$ at a center-of-mass energy of 4.26GeV using a 827pb$^{-1}$ data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be $(137\pm9\pm15)$pb. We observe a structure near the $(D^{*} \bar{D}^{*})^{\pm}$ threshold in the $π^\mp$ recoil mass spectrum, which we denote as the $Z^{\pm}_c(4025)$. The measured mass and width of the structure are $(4026.3\pm2.6\pm3.7)$MeV/c$^2$ and $(24.8\pm5.6\pm7.7)$MeV, respectively. Its production ratio $\frac{σ(e^+e^-\to Z^{\pm}_c(4025)π^\mp \to (D^{*} \bar{D}^{*})^{\pm} π^\mp)}{σ(e^+e^-\to (D^{*} \bar{D}^{*})^{\pm} π^\mp)}$ is determined to be $0.65\pm0.09\pm0.06$. The first uncertainties are statistical and the second are systematic.

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arXiv2014

Annealing Effect on Microstructure and Superconductivity of KxFeySe2 Synthesized by an Easy One-step Method

High-quality superconducting KxFeySe2 single crystals were synthesized using an easy one-step method. Detailed annealing studies were performed to make clear the phase formation process in KxFeySe2. Compatible observations were found in temperature-dependent X-ray diffraction patterns, back-scattered electron images and corresponding electromagnetic properties, which proved that good superconductivity performance was close related to the microstructure of superconducting component. Analysis based on the scaling behavior of flux pinning force indicated that the dominant pinning mechanism was delta(Tc) pinning and independent of connectivity. The annealing dynamics studies were also performed, which manifested that the humps in temperature-dependent resistance (RT) curves were induced by competition between the metallic/superconducting and the semiconducting/insulating phases.

cond-mat.supr-con↗

arXiv2014

Amplitude Analysis of the $D^+ \to K^0_S π^+ π^0$ Dalitz Plot

We perform an analysis of the $D^+ \to K^0_S π^+ π^0$ Dalitz plot using a data set of 2.92 fb$^{-1}$ of $e^+e^-$ collisions at the $ψ(3770)$ mass accumulated by the BESIII Experiment, in which 166694 candidate events are selected with a background of 15.1%. The Dalitz plot is found to be well-represented by a combination of six quasi-two-body decay channels ($K^0_Sρ^+$, $K^0_Sρ(1450)^+$, $\overline{K}^{*0}π^+$, $\overline{K}_0(1430)^0π^+$, $\overline{K}(1680)^0π^+$, $\overlineκ^0π^+$) plus a small non-resonant component. Using the fit fractions from this analysis, partial branching ratios are updated with higher precision than previous measurements.

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arXiv2014

Observation of $e^{+} e^{-} \to γX(3872)$ at BESIII

With data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.009 to 4.420 GeV, the process $e^{+} e^{-} \to γX(3872)$ is observed for the first time with a statistical significance of $6.3σ$. The measured mass of the $X(3872)$ is ($3871.9\pm 0.7_{\rm stat.}\pm 0.2_{\rm sys.}$) MeV/$c^2$, in agreement with previous measurements. Measurements of the product of the cross section $σ[e^{+} e^{-} \to γX(3872)]$ and the branching fraction $\mathcal{B}[X(3872) \to π^{+} π^{-} J/ψ]$ at center-of-mass energies 4.009, 4.229, 4.260, and 4.360 GeV are reported. Our measurements are consistent with expectations for the radiative transition process $Y(4260) \to γX(3872)$.

hep-ex↗

arXiv2013

Observation of a charged charmoniumlike structure Z_c(4020) and search for the Z_c(3900) in e+e- to pi+pi-h_c

We study e+e- --> pi+pi-h_c at center-of-mass energies from 3.90 GeV to 4.42 GeV using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies, and are found to be of the same order of magnitude as those of e+e- --> pi+pi-J/psi but with a different line shape. In the π^\pm h_c mass spectrum, a distinct structure, referred to as Z_c(4020), is observed at 4.02 GeV/c^2. The Z_c(4020) carries an electric charge and couples to charmonium. A fit to the π^\pm h_c invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9\pm 0.8\pm 2.7) MeV/c^2 and a width of (7.9\pm 2.7\pm 2.6) MeV for the Z_c(4020), where the first errors are statistical and the second systematic. No significant Z_c(3900) signal is observed, and upper limits on the Z_c(3900) production cross sections in π^\pm h_c at center-of-mass energies of 4.23 and 4.26 GeV are set.

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arXiv2013

Observation of a structure at 1.84 GeV/c$^2$ in the $3(π^+π^-)$ mass spectrum in $J/ψ\rightarrow γ3(π^+π^-)$ decays

With a sample of 225.3 million $J/ψ$ events taken with the BESIII detector, the decay $J/ψ\rightarrow γ3(π^+π^-)$ is analyzed. A structure at 1.84 GeV/c$^2$ is observed in the $3(π^+π^-)$ invariant mass spectrum with a statistical significance of 7.6$σ$ . The mass and width are measured to be $M=1842.2\pm 4.2^{+7.1}_{-2.6}$ MeV/c$^2$ and $Γ=83\pm 14 \pm 11$ MeV. The product branching fraction is determined to be $B(J/ψ\rightarrowγX(1840))\times B(X(1840)\rightarrow 3(π^+π^-))=(2.44\pm0.36^{+0.60}_{-0.74})\times 10^{-5}$. No $η^\prime$ signals are observed in the $3(π^+π^-)$ invariant mass spectrum, and the upper limit of the branching fraction for the decay $η^\prime\rightarrow 3(π^+π^-)$ is set to be $3.1\times10^{-5}$ at a 90% confidence level.

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arXiv2013

Observation of the decay $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{\pm}π^{\mp}+c.c.$

Using a sample of $1.06\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector, we present the first observation of the decays of $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{+}π^{-}+c.c.$ and $ψ(3686)$ $\rightarrow$ $Λ\barΣ^{-}π^{+}+c.c.$. The branching fractions are measured to be $\mathcal{B}(ψ(3686) \rightarrow Λ\barΣ^{+}π^{-} + c.c.)=(1.40\pm 0.03 \pm 0.13)\times10^{-4}$ and $\mathcal{B}(ψ(3686) \rightarrow Λ\barΣ^{-}π^{+}+c.c.)=(1.54\pm 0.04 \pm 0.13)\times10^{-4}$, where the first errors are statistical and the second ones systematic.

hep-ex↗

arXiv2013

Coexistence of two superconducting phases in Ca1-xLaxFe2As2

Single crystals of Ca1-xLaxFe2As2 for x ranging from 0 to 0.25 have been grown and characterized by structural, transport and magnetic measurements. Coexistence of two superconducting phases is observed, in which the low superconducting transition temperature (Tc) phase has Tc ~ 20 K, and the high Tc phase has Tc higher than 40 K. These data also delineate an x - T phase diagram in which the single magnetic/structural phase transition in undoped CaFe2As2 appears to split into two distinct phase transitions, both of which are suppressed with increasing La substitution. Superconductivity emerges when x is about 0.06 and coexists with the structural/magnetic transition until x is ~ 0.13. With increasing concentration of La, the structural/magnetic transition is totally suppressed, and Tc reaches its maximum value of about 45 K for 0.15 < x < 0.19. A domelike superconducting region is not observed in the phase diagram, however, because no obvious over-doping region can be found. Two superconducting phases coexist in the x - T phase diagram of Ca1-xLaxFe2As2. The formation of the two separate phases, as well as the origin of the high Tc in Ca1-xLaxFe2As2 is studied and discussed in detail.

cond-mat.supr-con↗

arXiv2013

Upper Critical Fields and Anisotropy of Ca1-xLaxFe2As2 Single Crystals

Superconductivity of Ca1-xLaxFe2As2 single crystals with various doping level were investigated via electromagnetic measurements for out-plane (H//c) and in-plane (H//ab) directions. Obvious double superconducting transitions, which can survive in magnetic fields up to several Tesla, were observed in the medium-doped (x = 0.13) sample. Two kinds of distinct Hc2 phase diagrams were established for the low superconducting phase with Tc lower than 15 K and the high superconducting phase with Tc of over 40 K, respectively. Both the two kinds of phase diagrams exist in the medium-doped sample. Unusual upward curvature near Tc was observed in Hc2 phase diagrams and analyzed in detail. Temperature dependences of anisotropy for different doping concentrations were obtained and compared. Both superconducting phases manifest extremely large anisotropies, which may originate from the interface or intercalation superconductivity.

cond-mat.supr-con↗

arXiv2013

Precision Measurements of ${\cal B}[ψ(3686) \to π^+π^- J/ψ]$ and ${\cal B}[J/ψ\to l^+l^-]$

Based on $(106.41 \pm 0.86)\times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, the branching fractions of $ψ(3686) \to π^+π^- J/ψ$, $J/ψ\to e^+e^- $, and $J/ψ\to μ^+μ^-$ are measured. We obtain ${\cal B}[ψ(3686) \to π^+π^-J/ψ]=(34.98\pm 0.02\pm 0.45)%$, ${\cal B}[J/ψ\to e^+e^-] = (5.983 \pm 0.007 \pm 0.037)%$ and ${\cal B}[J/ψ\to μ^+μ^-] = (5.973 \pm 0.007 \pm 0.038)%$. The measurement of ${\cal B}[ψ(3686) \to π^{+}π^{-}J/ψ]$ confirms the CLEO-c measurement, and is apparently larger than the others. The measured $J/ψ$ leptonic decay branching fractions agree with previous experiments within one standard deviation. These results lead to ${\cal B}[J/ψ\to l^+l^-] = (5.978 \pm 0.005 \pm 0.040)%$ by averaging over the $e^{+}e^{-}$ and $μ^{+}μ^{-}$ channels and a ratio of ${\cal B}[J/ψ\to e^+e^-] / {\cal B}[J/ψ\to μ^+μ^-] = 1.0017 \pm 0.0017 \pm 0.0033$, which tests $e$-$μ$ universality at the four tenths of a percent level. All the measurements presented in this paper are the most precise in the world to date.

hep-ex↗

arXiv2013

Study of $J/ψ\rightarrow ωp \bar{p}$ at BESIII

The decay $J/ψ\rightarrow ωp \bar{p}$ has been studied, using $225.3\times 10^{6}$ $J/ψ$ events accumulated at BESIII. No significant enhancement near the $p\bar{p}$ invariant-mass threshold (denoted as $X(p\bar{p})$) is observed. The upper limit of the branching fraction $\mathcal{B}(J/ψ\rightarrow ωX(p\bar{p}) \rightarrow ωp \bar{p})$ is determined to be $3.9\times10^{-6}$ at the 95% confidence level. The branching fraction of $J/ψ\rightarrow ωp \bar{p}$ is measured to be $\mathcal{B}(J/ψ\rightarrow ωp \bar{p}) =(9.0 \pm 0.2\ (\text{stat.})\pm 0.9\ (\text{syst.})) \times 10^{-4}$.

hep-ex↗

arXiv2013

Search for Baryonic Decays of ψ(3770) and ψ(4040)

By analyzing data samples of 2.9 fb^{-1} collected at \sqrt s=3.773 GeV, 482 pb^{-1} collected at \sqrt s=4.009 GeV and 67 pb^{-1} collected at \sqrt s=3.542, 3.554, 3.561, 3.600 and 3.650 GeV with the BESIII detector at the BEPCII storage ring, we search for ψ(3770) and ψ(4040) decay to baryonic final states, including Λ\barΛπ^+π^-, Λ\barΛπ^0, Λ\barΛη, Σ^+ \barΣ^-, Σ^0 \barΣ^0, Ξ^-\barΞ^+ and Ξ^0\barΞ^0 decays. None are observed, and upper limits are set at the 90% confidence level.

hep-ex↗

arXiv2013

Observation of a charged charmoniumlike structure in e+e- to pi+pi-J/psi at \sqrt{s}=4.26 GeV

We study the process e+e- to pi+pi-J/psi at a center-of-mass energy of 4.260 GeV using a 525 pb^{-1} data sample collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross section is measured to be (62.9\pm 1.9\pm 3.7) pb, consistent with the production of the Y(4260). We observe a structure at around 3.9 GeV/c^2 in the π^\pm J/psi mass spectrum, which we refer to as the Z_c(3900). If interpreted as a new particle, it is unusual in that it carries an electric charge and couples to charmonium. A fit to the π^\pm J/psi invariant mass spectrum, neglecting interference, results in a mass of (3899.0\pm 3.6\pm 4.9) MeV/c^2 and a width of (46\pm 10\pm 20) MeV. Its production ratio is measured to be R=\frac{σ(e+e- to π^\pm Z_c(3900)^\mp to pi+pi-J/psi))} {σ(e+e- to pi+pi-J/psi)}=(21.5\pm 3.3\pm 7.5)%. In all measurements the first errors are statistical and the second are systematic.

hep-ex↗

arXiv2013

Search for the Lepton Flavor Violation Process $J/ψ\to eμ$ at BESIII

We search for the lepton-flavor-violating decay of the $J/ψ$ into an electron and a muon using $(225.3\pm2.8)\times 10^{6}$ $J/ψ$ events collected with the BESIII detector at the BEPCII collider. Four candidate events are found in the signal region, consistent with background expectations. An upper limit on the branching fraction of $\mathcal{B}(J/ψ\to eμ)< 1.5 \times 10^{-7}$ (90% C.L.) is obtained.

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